Powerpoint template for scientific posters (Swarthmore College)

1
Population genetics in western garter
snakes Courtney Wolken¹, Megan Manes², Tonia
Schwartz², Anne Bronikowski² ¹Newton High
School, Newton, IA ²Department of Ecology,
Evolution, and Organismal Biology Iowa State
University, Ames, IA

• Results
• A total of 88 samples were successfully
  genotyped. (see Table 1)
• One locus was dropped from analysis because it
  was out of Hardy Weinberg equilibrium in all four
  populations.
• In comparing levels of genetic diversity, Stones
  (ST) had the lowest heterozygosity and fewest
  alleles.
• Fst values were significantly different among
  many locations. Stones had the most genetic
  divergence. (Table2)

• Questions
• Previous research has identified morphological
  and physiological differences between the
  ecotypes (Lakeshore versus Meadow), based on
  common garden experiments. This variation has
  both a genetic and environmental basis. We
  address the following questions as the first step
  to understanding the genetic basis for these
  differences.
• Do the populations vary in their amount of
  genetic diversity?
• 2. Are the populations genetically different?

• Conclusions
• We found significant genetic structure among the
  four populations.
• This structure was significant within the lake as
  well as between Lake and Meadow locations.
• The degree of structure was similar to the
  previous study on other locations around Eagle
  Lake.
• Of the four populations, Stones is the most
  genetically distinct and also has the least
  genetic diversity.
• Future Directions
• Extend the study to include four additional
  locations.
• Determine if multiple paternity is present in
  garter snakes, and if so, to what extent.
• Determine if the degree of multiple paternity in
  the studied populations of garter snakes is
  strongly linked to the life history traits
  defined by the differing ecotypes.

Introduction Eagle Lake, California provides
habitats for two different ecotypes of
terrestrial Gartner snake, Thamnophis elegans.
Based on location they have evolved differing
life history traits. Lakeshore ecotype fast
growth, early maturation, short lifespan, found
at low elevations Meadow ecotype slow growth,
late maturation, long lifespan, found at higher
elevations.

• Methods
• DNA was isolated from blood samples collected at
  four separate locations.
• Samples were Nanodropped to ensure proper
  concentrations of DNA.
• PCR reactions were run using eight different
  microsatellite loci with fluorescent-labels
  (neutral genetic markers).
• Gel electrophoresis was used to confirm a
  successful PCR reaction.
• Genotyping was performed by Iowa State University
  DNA facility and scored using Genemapper.
• Population parameters were calculated using
  Arlequin, Genepop, Genalex, and Structure.
• In testing each locus for Hardy Weinberg
  equilibrium, locus TelCa3 was dropped from the
  project.

Table 2 Pairwise Fst values indicates P-value
lt 0.01 indicates P-value lt 0.001
ML
SM

• Literature cited
• Manier, M.K. and Arnold S.J. 2006 Ecological
  correlates of population genetic structure a
  comparative approach using a vertebrate
  metacommunity.. Proc. R. Soc. B
• Uller, T. and Olsson M. 2008 Multiple paternity
  in reptiles patterns and processes. Molecular
  Ecology 17.
• Bronikowski, A. and Arnold S. 1999 The
  evolutionary ecology of life-history variation in
  the garter snake Thamnophis elegans. Ecology 80.
  

• Using Bayesian statistics, the program Structure
  was able to group the individuals into genetic
  populations (Fig. 2).

GAL
ST
Fig. 2. Graphical representation from
Structure. SM ST ML GA
Table 1. Sites, codes, ecotypes, sample sizes,
and measures of genetic diversity for the studied
locations. Ecotype refers to the habitat and
snake phenotype. L denotes a Lakeshore habitat, M
denotes a Meadow habitat
Fig. 1 (TOP) Ecotypes of garter snake found at
Eagle Lake. The checkered snake represents the
Lake Shore ecotype, the black and yellow striped
snake represents the Meadow Ecotype. (BOTTOM) Map
of locations in the study. Red dots denote the
lakeshore locations the blue dot denotes the
mountain meadow location.

• Acknowledgements
• NSF Plant Genome Research Program
• http//www.eeob.iastate.edu/faculty/BronikoA/homep
  age.html